Pala¨ontol Z (2011) 85:287–302 DOI 10.1007/s12542-010-0092-7 RESEARCH PAPER Belemnoid arm hooks from the Middle–Upper Albian boundary interval: taxonomy and palaeoecological significance Jens Lehmann • Alexandra Solarczyk • Oliver Friedrich Received: 9 July 2010 / Accepted: 15 December 2010 / Published online: 11 January 2011 Ó Springer-Verlag 2011 Abstract For the first time, a large number of belemnite The shift in belemnite abundance might be interpreted as arm hooks is described from the Lower Cretaceous triggered by a combination of warming and increased (Middle–Upper Albian boundary interval) of the classic productivity and/or condensation. locality of Folkestone in southern England. The arm hooks originate from six individual claystone layers; Keywords Belemnites Á Arm hooks Á Palaeotemperature Á some could have been attributed to the parataxon Arites Palaeoproductivity Á Cretaceous Á Albian Á England sp. Comparison is made with material from a drill core from Hannover, northern Germany that shows similarities Kurzfassung Erstmals wird eine gro¨ßere Anzahl von and also allows the description of a new parataxon: Belemniten-Armhaken aus der Unterkreide (Grenzbe- Hughowenites incurvatus n. gen. n. sp. The belemnite reich mittleres/oberes Alb) der klassischen Lokalita¨t hooks might belong to either the diplobelids Conoteuthis Folkestone in Su¨dengland beschrieben. Die Armhaken and Pavloviteuthis, both characterised by a reduced guard stammen aus sechs verschiedenen Tonsteinhorizonten, and thus very rare finds at Folkestone, or the abundant einige ko¨nnen dem Parataxon Arites sp. zugeordnet guard-bearing belemnitinid Neohibolites.Withinthe werden. Ein Vergleich mit Material aus einer Bohrung studied succession, belemnite hooks are more abundant in in Hannover, Norddeutschland, zeigt U¨ bereinstimmun- sediments deposited during an earliest Late Albian gen und fu¨hrt zudem zu der Beschreibung eines neuen warming event that is accompanied by an increased Parataxons: Hughowenites incurvatus n. gen. n. sp. Die abundance of guards of the belemnite Neohibolites. Belemnitenhaken du¨rften entweder von den Diplobe- Concurrently with this warming event primary produc- liden Conoteuthis und Pavloviteuthis stammen, die durch tivity was enhanced, as indicated by fluctuations in the ein reduziertes Rostrum charakterisiert sind und deren composition of the calcareous nannoplankton assemblage. Rostren deshalb in Folkestone sehr selten sind, oder dem sehr ha¨ufig auftretenden Rostrum-tragenden Be- lemnitiden Neohibolites. Innerhalb des untersuchten Profils sind Belemnitenhaken in Sedimenten, die wa¨h- rend eines Erwa¨rmungsereignisses im fru¨hen Oberalb J. Lehmann (&) Á A. Solarczyk abgelagert wurden am ha¨ufigsten, ein Zeitabschnitt der Fachbereich Geowissenschaften, Universita¨t Bremen, zudem durch das ha¨ufigere Auftreten von Belem- Klagenfurter Strasse, 28359 Bremen, Germany e-mail: [email protected] nitenrostren von Neohibolites charakterisiert wird. Parallel zur Erwa¨rmung war die Prima¨rproduktion er- A. Solarczyk e-mail: [email protected] ho¨ht, wie durch Ha¨ufigkeitsfluktuationen in den Verge- sellschaftungen indikativer kalkiger Nannoplanktonarten O. Friedrich belegt ist. Das vermehrte Auftreten von Belemniten Institut fu¨r Geowissenschaften, Facheinheit Pala¨ontologie, ko¨nnte durch eine Kombination von Erwa¨rmung und Goethe-Universita¨t Frankfurt, Altenho¨ferallee 1, 60438 Frankfurt/Main, Germany erho¨hter Produktivita¨t und/oder Kondensation erkla¨rt e-mail: [email protected] werden. 123 288 J. Lehmann et al. Schlu¨sselwo¨rter Belemniten Á Armhaken Á (Sellwood et al. 1994; Ditchfield et al. 1994; Pierri et al. Pala¨otemperatur Á Pala¨oproduktivita¨t Á Kreide Á Alb Á 1995; Price 1998), because belemnites are composed of England low-Mg calcite and thus the chance of preserving the ori- ginal carbonate is high (e.g. Marshall 1992). Belemnite values are nevertheless different from values obtained from Introduction other groups of organisms, and reasons for this remain unclear (Price 1998; Voigt et al. 2003). As an example, After the pioneering work of Neumayr (1883), who measurements obtained from the Late Cenomanian Actino- established faunal provinces and was among the first to link camax plenus indicate a cooler temperature compared with macrofossil distribution to climatic differences, it soon those from brachiopod shells from the same region or results became clear that many groups of Jurassic and Cretaceous obtained from modelling (Voigt et al. 2003). Hence, pal- belemnites show differing palaeogeographic distribution aeoceanographic interpretation is not unequivocal, and in patterns. In fact, belemnite faunas typifying the Boreal- this instance Voigt et al. (2003) propose either migration Arctic region can be distinguished from those characteri- from a cooler/deeper water mass or an unknown vital effect. sing the Tethyan region (e.g. Stevens 1963; Combe´morel Nevertheless, geochemical data derived from belemnite et al. 1981; Mutterlose 1986; Doyle 1992; Gale and rostra constitute important data for the palaeoclimatologic Christensen 1996; Alsen and Mutterlose 2009; Wilmsen interpretation of belemnites. et al. 2010). Several decades ago it became clear that These different approaches show that belemnite data are generalisations about the palaeotemperature preferences of useful for reconstructing palaeoclimates with respect to belemnite higher taxa are not possible (e.g. Stevens 1965). palaeoceanography. However, the classical approach in Different belemnite families and genera show different directly relating the distribution of belemnite guards to temperature tolerances, while the temperature preference climatic factors is naturally limited in its argumentation, of some belemnite groups changed during their evolution. and a number of contradictions still cannot be explained The Tethyan belemnopseid Hibolites, for example, is (e.g. Doyle and Pirrie 1999). Therefore, further environmental regarded as ancestral to the important Boreal family Be- factors have been considered to avoid the over-simplification lemnitellidae as well as the southern endemic stock of the that water temperature had the major biogeographical control Dimitobelidae (Doyle 1987a; Doyle 1987b; Christensen on distribution patterns. These factors include changing 1988), therefore indicating a significant evolutionary oceanography and physical barriers, water depth and salinity change in temperature sensitivity. Changing palaeotem- (Doyle 1988). Here, we test these different hypotheses by perature tolerance can also be traced at lower taxonomic investigating the immediate response of belemnites to a dis- levels, as in the case of the widespread Aptian-Albian crete, short-term climatic warming event that is known from a emigration from the Tethys by the belemnopseid Neohib- number of further proxies besides the belemnite data them- olites (Doyle 1987b). Based on palaeobiogeographical selves. We use belemnite hooks obtained from washed clay- patterns, Mutterlose et al. (1983) were able to distinguish stone samples for this innovative approach. between eurythermal and stenothermal belemnite genera in the Early Cretaceous. Hibolites and Neohibolites are eurythermal warm-water genera with high potential for Locality details and methods thermal adaption that occurred in the Boreal as well as in the Tethys, whereas Duvalia, Berriasibelus and Parahib- The present paper deals mainly with a series of samples olites, among others, are stenothermal warm-water genera from the classical section near Folkestone, southeastern that are limited to the Tethyan realm (Mutterlose et al. England, that is located in the Anglo-Paris Basin (Fig. 1). 1983). Additionally, test samples and single specimens originating Use of carbonate oxygen isotope ratios in belemnite from the Hannover area in northwestern Germany (Lower guards for estimating palaeotemperatures sheds new light Saxony Basin) have been considered, a region that showed on belemnite palaeoecology and allows their application as an open shelf connection to the Anglo-Paris Basin (Fig. 1). palaeoclimatological and palaeoceanographical proxies (e.g. Bodylevskii 1957; Tejs and Naidin 1969; Wefer and Folkestone section Berger 1991; Price 1998). In the early years of isotope analysis, belemnite rostra were regarded as imperfect Important accounts of the research history of the classical sources for deriving palaeotemperature estimates, since it Gault Clay section (Middle–Upper Albian) at Copt Point, was thought that there might be a high ratio of secondary East Cliff, Folkestone have been provided by early authors cement, leading to alteration of the primary signal (e.g. such as Parkinson (1819), Fitton (1836), De Rance (1868) Wefer 1982). These doubts largely have proved unfounded and Price (1874) and, more recently, by Casey (1966) and 123 Belemnoid arm hooks from the Middle–Upper Albian boundary interval 289 Fig. 1 Palaeogeography of the early Late Albian in northern Europe with localities and areas mentioned in the text. Localities: Fs Folkestone, Kent; As Ashford, Kent; HL drilling core in Hannover-Lahe, Lower Saxony; Ah O¨ lbach stream cut S of Ahaus, Northrhine- Westphalia. APB Anglo-Paris Basin, LSB Lower Saxony Basin. Map modified after Ziegler (1982, 1990) Owen (1971a, b). In particular the outstanding preservation point in the cliff at 51° 502.6200N, 01°11057.9500E was recorded of ammonites, including their iridescent shells, is famous using GPS and is documented in Fig. 2. Each sample was